离子液体电沉积资源化硅业副产物氯硅烷及其回收物在硅薄膜太阳电池上循环再利用的基础研究

With the rapid development of the silicon industry, the amounts of chlorosilane byproducts of silicon industry are dramatically increasing. It will cause serious environmental problems without proper disposal. To develop a highly effective and environmentally and safe technology to utilize chlorosilane is becoming an urgent problem.Considering the good solubility of chlorosilane in ionic liquid and the distinguish electrochemical properties of ionic liquid, it may be a cost-effective method to extract silicon from waste chlorosilane by electrochemical processes in ionic liquid. According to the studies on the regularities and principles of silicon tetrachloride's dissolution in ionic liquids, the byproduct chlorosilane are dissolved and purified through the optimization of the ionic liquid design. Based on the investigation of the ionic liquid's characters and the effect of impurities on the quality of silicon electrodeposited, methods for regulating the composition and crystal morphologies of deposited silicon are explored. In situ doping to growth n-type and p-type silicon layer which can be used for the preparation of nanocrystalline silicon thin film solar cells are studied by electrodeposition in ionic liquid. In this study, a high-value utilization process for harmless recovering the byproduct chlorosilane can be developed, and scientific basis for efficient utilization of the similar waste to chlorosilane can be provided.

氯硅烷是硅产业的主要副产物，产量大且污染严重，但同时其也是一种宝贵的硅资源。本项目面向氯硅烷高效清洁处理与硅基电池原材料低成本技术创新的迫切需求，根据离子液体能溶解氯硅烷并具有良好电化学性能的特点，拟采用离子液体电沉积法回收氯硅烷并提取其中的硅资源。采用分子动力学模拟方法研究氯硅烷在离子液体中溶解解析的耦合机理；将离子液体的黏度、电导率、电极电势和电化学窗口等电化学物性与量子化学计算获得的电子性质、前线轨道等结构信息进行关联，设计和筛选出适合氯硅烷溶解和电沉积的离子液体；研究氯硅烷-离子液体体系中硅的电沉积机理及硅成分和晶态的调控方法；探索离子液体在氯硅烷溶解-电沉积过程中的循化利用方法；通过离子液体电沉积实时掺杂制备n、p 型硅掺杂层用于纳米硅薄膜太阳电池。通过多学科交叉为硅业副产物氯硅烷的高值资源化和无害化处理提供新的技术途径，同时将为该类危险废物的处理提供必要的应用基础性科学依据。

本项目采用离子液体电沉积法回收四氯化硅并提取其中的硅资源。用COSMO-RS方法模拟预测四氯化硅在不同离子液体中的亨利系数，并用GEMC模拟两相平衡的方法来计算溶解度；筛选出了咪唑类、吡啶类和季铵盐类共3类10种离子液体进行SiCl4的溶解实验，探究了其溶解性变化规律；选择[Bmim]NTf2和[N1114][TNf2]两种离子液体进行SiCl4的电沉积实验研究，对电沉积硅薄膜结构特性、光学性质及电学性质进行了分析，并研究了杂质对电沉积过程的影响及离子液体的循环性能。结果表明：SiCl4在离子液体中的溶解量随着温度的上升而下降，离子液体阳离子烷基链长越长对SiCl4的溶解效果越好。Raman光谱表明，离子液体和SiCl4间以C-Si键、C-Cl键和Si-O键相连；钛片为工作电极，SiCl4浓度为0.35mol/L、IL：PC=1:2、电流密度为40A/m2时电沉积效果较好，所得沉积产物为非晶硅，光学和电学性质较好，但由于空气存在，表面硅层被氧化为SiO2，产物成分为Si和SiO2共存；以液态金属镓（Ga）作为工作电极时，100℃条件下电沉积能产生较为完美的多晶硅薄膜；当副产物中Ti、Al、Fe、V和SiHCl3等杂质含量在2%和3.5%以下时，不影响非晶硅的生成；以-3V电压通电10小时后，离子液体的性质未发生明显改变，FT-IR谱图结果显示其结构并未破坏，并且利用其电沉积硅取得了较好效果，循环性能较好。项目研究成果为硅业副产物四氯化硅的离子液体电沉积资源化提供了科学依据和技术支持。